omenti

the golden albatross and eternity

 Astronomy was where America began to emerge from European domination of science.   The wealthy patrons who funded telescopes and universities made certain the discoveries were heavily publicized.  Even out in Kansas Clyde Tombaugh found his interest.  He did well inscience and math student and dreamt of leaving the farm for the University of Kansas.  

 

Then the hail came.. 

 

Spend any time in the Midwest or West and you'll see the hail shafts associated with violent thunderstorms.  I found them beautiful until I saw the crop damage at the farm of a family friend - two weeks before harvest and most of his Winter wheat gone in a few minutes.  They had crop insurance.  No one did in Clyde's time.  He wasn't going to college.  

 

He spent time in the library reading every about astronomy and came across one of the amateur telescope making books.  Athletes with exceptional ball control are said to have "good hands."  In telescope making it means you can make a parabolic mirror with that is accurate to a fraction of a wavelength of light across it's surface.  It takes patience and skill - I made one as a teen that, well, let's just say I didn't have good hands,. 

 

The Tombaugh farm was dark - many parts of the state hadn't seen electricity to the farm yet. He set himself to observation paying particular attention to Jupiter.  Amateur astrophotography wasn't useful yet, so you made pencil drawings.  Clyde's were beautiful and accurate.  He had the ability to look at Jupiter for long periods and mentally subtract out some of the atmospheric distortion - a hallmark of the best observers of the day.  He was a natural.

 

In 1929 he sent a packet of his drawings to the Lowell Observatory asking if they could use someone like him.  It arrived completely out of the blue.  It turns out they were excited..  but perhaps for a different reason.

 

Percival Lowell was the scion of Boston's Lowell family.  He went the Harvard route with interests in the Far East, astronomy and math.  With serious money at his command he built a state-of the art observatory in Flagstaff, New Mexico and set about studying Mars.  His telescope wasn't good enough to accurately show the features of Mars, but good enough to give hints.  His imagination enhanced his drawings and an elaborate canal system emerged.  A system that changed with the seasons.  Astronomers, some armed with comparable telescopes and a good deal more experience, considered it poppycock, but the press went nuts.  Early science fiction and even a few religions had people excited about life on the Moon and nearby planets.  Did you know the men and women who inhabited the Moon stood over six feet tall and were covered with fur, or that Martians were under three feet tall with huge eyes and a greenish, hairless skin?  It sold a lot of newspapers and dime novels and perhaps got kids reading.   There was even this writer, HG Wells, whose fleshing out the pseudoscience of the day became art.

 

Shortly after the dawn of the 20^th century Lowell had been thrououghly debunked by astronomers with better telescopes and astrophotographs.  Undaunted and wanting to save his reputation. he turned his attention to Planet X - a conjecture that a planet existed beyond Neptune.   He had noticed irregularities in the orbits of Nepture and Uranus and, from that, make predictions of where a mass - a planet - might be.  The word planet goes at least as far back as the Greeks and means wanderer.  A planet appears to move relative to the stars.   The hunt involved taking high quality photographic plates of interesting areas of the sky.  Later he'd photograph the same areas and look for the differences.  You take advantage of a neat little feature of human vision.

 

If you look at two identical slides with images on them - one through each eye - and flash a light at the same rate behind each, you get a single flashing image. But if anything is different on one of the plates -- say one of the little dots has moved - you see it blink.  We're spectacularly good at this.   Lowell spent ten years observing and using his blink comparator, but nothing.

 

His will was generous with the observatory. They could embark on new missions and expand.  But there was this one little problem -- the will specified they had to continue the search for Planet X.  Most professional astronomers thought this a wild goose chase.  The observatory had been fitted with a golden albatross. 

 

Tombaugh's letter arrived out of the blue in the late 20s.  The images were at the limit of what one would expect from a telescope that size. They immediately recognized the work of someone with enormous patience and exceptional integrity.  Someone who could rid them of the golden albatross.

 

They'd set him up in a corner by himself with a small patrol telescope.  He'd photograph at night and search on the blink comparator during the day.  They figured he'd do it until he got bored - maybe even the rest of his life - and he wouldn't embarass them.  They'd be free of the goose chase and could get on with real science.

 

Clyde surprised them.  On the 18^th of February in 1930 there was a tiny blinking dot.  It was confirmed on other days and an orbit calculated.  It wasn't possible to calculate the mass at the time - Lowell had predicted a heavy body - but the tiny dot was in about the right place.

 

Maybe it was that delightful bright note during that came during the Winter of the beginning of the Depression, but the discovery gripped the public imagination and was featured in newsreels that were shown with movies.  Clyde became a national hero - farmboy from Kansas discovers a planet perhaps as big as Jupiter and well beyond Nepture.. or so said the headlines.  People wrote in with names.

 

The astronomy community wasn't buying it.  The orbit wasn't in the ecliptic - the plane of the rotation of the Sun and the orbits of all of the other planets.  They thought he found a trans Neptunian object.    But astronomy had become hot and contributions were finding their way to university astronomy departments in a depression.  Collectively the community sighed and sat on it.

 

Pluto's discoverer finally made it to the University of Kansas earning bachelor's and master's degrees in astronomy. Imagine what it must have been like for his first astronomy professor to have him as a student.  This person who had popularized astronomy far more than any professional.   After WII Clyde taught astronomy at New Mexico State until his retirement.   Throughout his life he did fine work popularizing this passion of his. 

 

Lowell's calculation was flawed.  This Pluto thing, note that PL are his initials,  just happened to be about in the right place and one of the few people who could have discovered it at the time was on the case.  It wasn't until the late 70s when Pluto's mass could be reliably calculated - it turns out to be small.  It was an amazing find.

 

serendipity is the word that comes to mind

 

I know this guy who works in Pasadena who decided to make a case that Pluto wasn't a planet. He calls himself Pluto Killer.  He specializes in trans-Neptunian objects and Kuiper Belt Objects.  New definitions were needed to describe the rich weirdness that was turning up.  Pluto may not be a planet, but it is awfully interesting.  Then a guy at the Hayden Planetarium took up the cause.  Imagine Neil deGrasse Tyson getting hate mail.  And from school children.  For whatever reason people wanted Pluto to remain a planet.   They lost.  Now Mike has predicted his own Planet X.  Now more than a few are looking and people suggest names to him. 

 

 
About two years ago the  New Horizons spacecraft flew by Pluto sending back a treasure of information  images that raises questions no one imagined.  The images are amazing - hunt a few down. Now it's on it's way to Kuiper Belt Object.   From there it's straight on to eternity.    

 

There's a small container inside.¹ The inscription says:

Interred herein are remains of American Clyde W. Tombaugh, discoverer of Pluto and the solar system's 'third zone'. Adelle and Muron's boy, Patricia's husband, Annette and Alden's father, astronomer, teacher, punster, and friend: Clyde W. Tombaugh (1906–1997)

 

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¹ I find astronomy to be the most romantic of the sciences and astronomers to be the most romantic of the scientists.  Hard rockers are the most gonzo, biochemists the most integrative, climatologists and oceanographers the most dedicated to the planet, but romantic --  that's astronomers.  

At JPL on the day of the flyby several people wore simple t-shirts that said godspeed clyde tombaugh

 

 

 

 

 

__________

tips you can use:

 

For those of you (like me) who still have corded earbuds there's a neat trick to minimize tangles.  Most people simply wind the cord around their fingers.  The problem is unidirectional winding introduces twists (try it with a flat ribbon).  If you wind in a figure eight pattern you make a twist and then add another that turns in the opposite direction.  They cancel each other.   Just drop the cord between your middle fingers and wind about.  When you're done secure the middle with a little clip.  

 

I've been doing this since my undergrad days.  It's a good way to spot physicists and mathematicians. 

 

 

 

 

 

G, A, F, ↓F, C

just kidding .. well .. sort of..

 

About a month ago I noticed my left shin and foot had swollen enormously.  There are a few nasty possibilities and a close friend died from one in December, so it was off to the emergency care unit.  It turned out to be something easy to deal with, but the exams were interesting. I have this fascination for instrumentation and had a nice conversation with the ultrasound operator.  He didn't know what one of the settings on his machine was doing.  The name was a giveaway so we talked.  In return he gave me a detailed tour of the innards of my legs (good and bad one) and a few other places too.  The interface was aimed at experts, but very interesting.  He had a rich menu of information to display on the screen - often images and graphs. He could also choose to represent some of then acoustically over speakers or earphones.    He said he almost always used the visual displays along with simultaneous audio as combining the channels was much more informative than either alone.   It took me back to my first big particle physics experiment.

 

 

At a conceptual level particle physics is easy - smash particles together and sort through the debris.  The problem is the easy stuff's been done.  More exotic interactions are rare and happen at energies high enough that most of the interactions are complicated mixes of well studied results.  All of this happens at a furious rate much higher than is encountered anywhere else - there is no way to save all of the data you're measuring. You need to be able to throw away what isn't interesting while keeping the tiny bit that is.  When I started we kept one in a few thousand events.  Now some of the larger experiments are more like one in a million.   This is done with with triggers.

 

Triggers are logical groupings of signals that give you an early hint, think a hundred nanoseconds or so, that something is candidate for further study.  Conceptually it's something like this  electron over a certain energy hits this part of your detector, this other part of the detector is completely quiet, and another particle  is coming out at nearly a right angle to everything else. It may or may not be real - that's for further study, but  it happens it's worth saving.  The trigger fires and you save it.  We had about a dozen triggers.  It was often convenient to look at an event soon it took place to learn about your experiment and possibly even find a hint of something interesting.   That's where the title of the post comes in.

 

A few years before this experiment  I had seen Close Encounters of the Third Kind.  A meh as a film, but the music caught my attention.    The aliens used music to communicate.  To signal them, scientists sent played five notes:  G, A, F, F (an octave down) and C. 

 

five tones

 

When the spacecraft arrives they used a variation on the theme and the aliens respond.  Then something of a jam session takes place.   

 

Designing my triggers it struck me that some had cluster groupings in the detector  that could be expressed as a unique three note cord.  I knew about synthesizer music (Switched on Bach and Walter/Wendy Carlos) and sort of borrowed a dozen frequency generators from the undergrad teaching lab (they had a lot of them).  A bit of tuning and I had a full musical scale.  Some of the most important triggers were F major (F-A-C), C major (C-E-G), and D major (D-F#-A) .. there were a couple of minor chords.  It worked and proved itself.  It was my gateway drug -  I've been interested in sound as data and as a computer-human interface ever since.  Data sonification can be a nice way to handle human data overload. We seem to be wired for it (some of us more than others), but modern interfaces rarely use it. 

 

Then there's listening...

 

Imagine a manager stepping onto a railing overlooking the production floor in a 19^th century textile mill. He (sadly always a he) would look around, listen and maybe even smell.  Machines slightly out of spec would stand out ..  a sour note in the harmony.  Moving forward most car mechanics use sound as a diagnostic tool and even listen to customer renditions to narrow the problem space.  I use it to sort out issues with the washing machine and dryer - usually as a diagnostic tool when something breaks, but I'm beginning to use it as an indicator of future failure.   

 

Consider mechanical devices that may be difficult to fully incorporate into data analysis programs.  A feature of mechanical devices is the units of the same model are unique.  An xyx -102 refrigerator in your home probably has somewhat different operating characteristics than the same model in your neighbor's home.  Monitoring such devices and feeding using the information for optimal efficiency and lifetime can be difficult - especially on older existing hardware.  A good example are chillers used in building-scale cooling.  Their efficiency improves with increasing load - often dramatically until you reach a point where the unit shakes and is in danger of failing.  Each chiller is different.  A human operator usually is in charge of several and learns about their individual quirks.  A lot of valuable information - often hundreds of thousands of dollars worth - is locked up in a few local experts.  An expert from a different building would have a learning curve.  Bringing information out of the the human is a major challenge.  You have to be clever. You spend a lot of time with chillers.

 

A neat trick is to study the acoustic signature of chillers as they approach and go through their point of maximum efficiency.  They begin to emit a banging sound that changes to a screeching noise.  They shake on their mounts.  If you can begin to detect this you can back them off a bit and stay near their maximum efficiency while prolonging their life.  The easiest way is a microphone or a vibration sensor (which is all a microphone is).  It is pretty simple to digitize this and move it into a computer than can offer feedback to the machine control.¹  It can also feed into a machine learning program so you can begin to characterize all of your chillers prolonging their lives and predicting when they will fail so maintenance takes the place of failure.  

 

Getting data about the world around us can take a wide variety of sensors, but shortcuts are emerging.  Cameras output images, but add a computer and they can do quite a bit more: image recognition, crop analysis, temperature (infrared cameras) ... the list is dramatically expanding.   We mostly neglect sound, but microphones are a simple and often inexpensive sensor that with a computer can do much more.  Data streams from these powerful computational enhanced sensors can be integrated with other data streams for real machine learning.  Opportunistic data hunting.

 

I have a few of personal interests along these lines.  One is the acoustic ecosystem signature of ecosystems.  The local woods have coywolves.  I've put digital recorders out there just to capture their howls, but it is clear the background sounds might be important.  Flora and fauna have their own signatures spanning large frequency and time domains.  This is probably near ground floor fun for amateur scientists.  I can even imagine it being useful in many sports.

 

Now think about other senses - there are many more than five.

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¹ An Arduino and a piezoelectric buzzer/speaker used as a microphone is probably overkill for an application like this. 

 

 

50 miles on a pint of peanut oil

When I was a kid my Dad would bring comic books home.  My favorite involved the Donald Duck series character Gyro Gearloose.  Gryo was a brilliant semi-failed inventor for hire with offbeat ideas that I loved.  I wanted to be Gyro when I grew up - I even pestered my parents for round glasses (I didn't get them)One was a flying scooter that got 50 miles to a pint of peanut oil.  A flying scooter was a neat idea, but the number stuck with me - 400 miles per gallon.  

 

At the time the family car was a very inefficient station wagon that got about 12 or 13 miles per gallon in highway driving.  It would be replaced by a very light Ford Falcon that reached the then almost unimaginable 20 mile per gallon level.  About the same time I got my first real bicycle - a three speed "English Racer" from Raleigh.  It was used, but Mrs Isler at Isler's Bicycle refurbished second hand bikes in addition to selling new Schwinns and Raleighs that were beyond my means. 

 

The black Raleigh lasted a few years before I need to move on.  I took care of it, but it was used at least nine months out of the year and was showing its age.  That and consumer bike tech was changing. I'd go down the Isler's and drool.  Sting Rays and then ten speeds.  She had a derailleur mechanism set up that you could hand crank and physically feel the effect of using different gears.  In ninth grade I finally got a bright blue Schwinn ten speed.  Five hundred dollars in today's money -not the top of the line, but still and object of desire.  It took longer, but I wore it out too - the rocket assist experiments probably didn't help much.

 

Bikes were becoming a thing nationally.  I started college at the University of Utah.  There were at least three bike shops in nearby, bike racks everywhere on campus and at least a half dozen sheds with compressed air and tools for quick bike repairs.    Later I moved to Pasadena and found bikes everywhere at Caltech too..  I moved on to a hand built Raleigh Professional which is still a thing of beauty.  In fact they were on the rise across the US and in Northern Europe. The second great bicycle revolution was underway.

 

The first came with the invention of the safety bike.  Starting around 1890 bicycles came on the scene in large numbers.  Roads were built and a manufacturing industry was born.  The boom lasted about twenty years.  Kids still used bikes, but the automobile was becoming practical and large sums  were going into automotive infrastructure.  Bike makers moved into automobiles and airplanes.

 

The second boom was sparked by better tires and inexpensive and reliable gearing systems - at least on the technical side.  The social and infrastructure components were more complex and interesting.  Sort of book length interesting so I'll give the abridged version:

 

 Denmark and the Netherlands saw cycling as important for very different reasons, but supported it with policy and infrastructure.  Public acceptance was slow, but by the 90s both countries had  successfully integrated cycling into their transportation systems. The boom in the US and UK died.  Cycling in the US survived as a recreational sport with a very small and very male portion of the population.  Children still learned how to ride bikes, but the movement of controlling the activities of children killed the the notion of using them for transportation.  Bike racks disappeared from schools and many considered bikes dangerous.

 

We're beginning to what some - Horace Dediu and I are in the camp - would consider a third revolution.¹  This one is a bit different.  It's concerned with efficiency.  How do you move someone around efficiently?  The answers are complex and involve far more than just the vehicle, although aspects of the vehicle suggest pathway.  You may have a thirty minute commute - that's pretty standard and has been for decades..  people often live in places that give them thirty to sixty minutes of commuting.  The percentage of commutes longer rapidly drops at longer commutes.  The day only has so many hours.  One the other hand an analysis of most trips shows a number of smaller trips are very common.   Anything under about four or five miles is rich bicycle territory.  Why use a car?

 

Let's take a diversion and talk about efficiency. .  Electric drive trains are much more efficient than the best internal combustion drive trains ..  about three times as efficient (nearly three quarters of the gas you buy heats up your engine block and that won't get much better).  Electrics are efficient, batteries are dropping in price and charging infrastructure is improving.  Sweet - but the vehicle is still a car.  One and a half to two tons hauling around one person and a few groceries.   Something is broken.

 

Here's were something like a bike comes back in.  A few years ago and friend and I measured her efficiency on a bike.  We measured how many Joules she "burned"to go a fixed distance and converted it into MPG_e - miles per gallon equivalent.²    

 

She got slightly over 1,000 MPG_e at about 13 miles per hour on flat ground.  She's very tall and her coefficient of drag in the upright position is - well - not good.  In a racing position she's probably be over 1,100 MPG_e. 

here's a little conversion table

 

1 MPG_e ~ 0.013km/MJ

                   0.0478 km/kWh

                   1 mi/33.7 kWh

                   0.0297 mi/kWh

 

so convert away...

 

It varies with formulation, but MPG_e assumes a gallon of gasoline has about 33.7 kilowatt hours of energy.  It also happens to be very close to the energy density of diesel fuel and  - well  - peanut oil.  So if she was drinking peanut oil, she'd be well over Gyro's number.   If she had something like Ben and Jerry's she'd be closer to 300 MPG_b&j..  and that seems a bit more fun.

 

Riding a bike is terrific exercise, but it may be too much if you have hills, longer distances or not much time.  This is where a human-electric hybrid comes in (they go by several names).  Normal riding on a bike uses about 100 watts of muscle power.  With an ebike you still supply muscle power , but an electric motor augments your pedaling with 25 to several hundred watts depending on your taste.  You're still getting exercise, but now you're producing power on the order of a Tour rider or better.  You have become superman or superwoman.  The feeling is quite amazing.

 

I built one in the mid 80s trying to crack 2,000 MPG_e ..  It was a primitive hack, but I managed 2,300 MPGe.  A good ebike starts at about $3,000 and go up, but large scale production would dramatically drop the price.  

 

I'm skipping over a lot, but you need infrastructure and a cultural acceptance to make cycling part of an efficient transport system.  Outside of a few regions I'm not sure how successfully those issues can be addressed in the US, but much of the rest of the world is ripe.  And in the US some small cities (say under 100,000 population) and suburbs may be fertile ground for female riders... people who want transportation rather than a toys.³  That means moving something besides themselves.  This is where an ebike can shine, but the design diverges from what one normally thinks about.    A friend who is heavily into bikes as transportation in a Denver suburb sent this link of her new "crossover" - a practical electric cargo bike designed with women in mind.  

 

There are so many other aspects to this, but pencils down - my hour's up.

 __________

¹ Horace is a very clear thinker.  You really should follow him ..  he's also at Asymco. 

² It's only meaningful in the US as most people here think in terms of miles per gallon rather than something like liters per hundred kilometers... they're measuring the same thing, but I'll use MPG_e. When I'm doing physics I'm usually in joules or electron volts.  If it's human scale energy, I usually use watt-hours.  Whatever is convenient. 

³ Women are bicycling's indicator species

 

 Derailleur

serving pancakes to the moon

Ah total solar eclipses.  My first was somewhat East of Lewistown, Montana after driving in the dark on an icy Highway 87.  The Sun had just set on all of the horizons around me when the sonic boom arrived .  I looked up and saw a delta wing, afterburner blazing in the starry sky, streaking Eastward.  Returning to the main event I remember thinking "oh my god - the best seat in the world!" 

 

Fellow Montanan Jeri sent this after last week's eclipse note:

 

Check out yesterday (Sunday's) GF Trib. My brother-in-law is on front page flying an F106 at 1200 mph chasing the 1979 eclipse: Major Don Stevlingson. Can you imagine?

 

 Wow!

 

The Sun's diameter just happens be about 600 times that of the Moon - almost exactly how much further away the Sun is than the Moon.   The Moon's orbit is eccentric enough that sometimes it's apparent size isn't quite enough to cover the Sun and we get an annular eclipse.  If it's close enough - and our orbit around the Sun is also a bit eccentric so just how close varies - totality ranges from a very short time up to almost seven and a half minutes.  

 

You need to see a total solar eclipse at some point in your life!  If you can't make it to this one (sadly that includes me) there are a variety to chose from around the world - about two per year of varying quality.  The next big North American eclipse move in the US around Austin, Texas and arcs up to the Northeast on 8 April, 2024.  You might make hotel arrangements now.

 

Back to the post. So how do you measure the distance to the Moon?  

 

You may have done it in your first trigonometry class - it's a simple parallax calculation.   The problem is making a careful enough measurement.  And being careful you need to understand your measurement well enough to be able to estimate the error of your result.

 

 Ah data...

 

One of the attractions of physics is the core ideas and even experiments are conceptually very simple.  Execution gets a bit involved, but that's part of the fun.  You have to understand your data and what happens to it at every step.   I've been meaning to talk  about measurement and data - the provenance and handling of data and data quality.   So why not an example of how you'd measure the distance to the Moon today.

 

You've probably gone out, flashlight in hand,  on a dark Summer night.  You find your way, see the trees in a new way and perhaps see the eyes of skunk or deer.  Looking up at the stars you find yourself pointing the flashlight skyward.  Sometimes  dust or bugs in the air makes the beam visible.  Up, up and up until it disappears moving at the speed of light.  You point it at a star and wonder how long 'til the light gets there.¹   Now if you could put a mirror out there and had a good stopwatch you could measure the distance.

 

This is at the core of how a physicist (and probably many in other natural sciences) thinks - thought or gedanken experiments.  You make a concept as simple as possible so you can play with it in your mind.  You quickly learn if it's nutty or worth pursuing.  

 

This one's worth the effort.  Thanks to American and Russian space programs there are four special mirrors on the Moon.  Each is an array of corner reflectors that bounce a beam of light back in the direction it came.  The speed of light is about 186,000 miles per second and the Moon is about 240,000 miles away so a round trip is about two and a half seconds. 

 

And if it worked ideally

 

 (I love xkcd)

 

You can do this with laser, telescope and detector.  In fact kit in most University physics department would work or you could buy your own for about the price of a sports sedan.  Unfortunately it's just fun to show you can bounce light off a mirror on the Moon.  The accuracy isn't good enough to answer interesting questions like how fast is the Moon moving away from us (tides are causing it to slowly spiral out) or testing the validity of theories about gravity like General Relativity. 

 

Now you get out the chalk and work out something a bit more realisitic

 

You want to send out a boatload of photons of light.  Light travels about eight inches every nanosecond (billionth of a second), so the pulse should be short and your stop watch should be good.   A garden variety atomic clock is just fine.  And a laser comes to mind as they tend to produce very directional beams of light.  Unfortunately any beam of light diverges thanks to atmospheric turbulence.  The best you can do is a beam that spreads out at an angle of a second of arc - about three ten-thousands of a degree.  To put things in perspective think about a quarter five kilometers (three miles sort of) away or a volleyball at about 130 kilometers.  It doesn't seem like much, but the Moon is more than a bit farther out.²

 

The return trip is worse.   The retroreflectors spread light about eight times more than our atmosphere.  You want a great detector and a very bright source.  The best measurements are done using a big telescope to make the light as parallel as possible going out and to collect as much as possible coming back.  The mirror is 3.5 meters in diameter and the laser makes a short bright pulse that lasts slightly under a tenth of a billionth of a second - about the time it takes light to travel about an inch.

 

You're serving the Moon pancakes of light 3.5 meters across and three centimeters thick with a fantastic laser pointer.³

 

Now some numbers.  Due to beam spreading only one  in 30 million photons in the pancake make it to the mirror array on the Moon and about one in 30 million will make it back to the telescope.   Each pulse puts out enough photons that a handful come back. This is fewer than you'd expect from the simple model so far.  You have to consider absorption and scattering in the atmosphere and the efficiencies of the detectors and mirrors.  Accurate predictions very difficult, but we're more interested in time of flight.  All we really need to know about efficiency is do we have enough make good measurements.  

 

This is an important feature of data.  Required accuracy and error measurements depend on what you're doing.  It's good form to work out the errors for everything in case someone comes along later and wants to use what you did for something you may not have thought about. 

 

Going deeper there are some problems you must recon with if the measurement is going to be accurate to anything better than the length of a football field.  

 

° light travels more slowly in the atmosphere than it does in space.

° the density of the atmosphere drops dramatically with altitude and varies on short time scales

° the real distance to the Moon is constantly changing since the Earth and Moon are in relative motion and since the Earth rotates at about 400 meters per second at the latitude of the observatory.  Add these up and the distance between the observatory and the Moon is changing at hundreds of meters per second - and you're worried about a roughly two and a half second roundtrip.

 

See - there's a reason for starting at a simple conceptual level before diving in.  

 

There are techniques for handling these, but you need to know the errors and propagate them into your final result.  Every step along the way and the changes over time.  There is a provenance and a history associated with data that must be known or it is worthless.   Getting bitten is all too easy - every experimentalist can tell you horror stories - so you have to verify each step.  Sadly not all big data work I've seen is very carefully done and has hidden issues.

 

It is common for repeated experiments to not give the same result.  This can be a good thing as it tells you something about the two different measurements - there may be something new or perhaps a better technique.  You learn a lot from failure.  Life gets ugly when the core measurements have large errors as is common in medicine and the social sciences.  Unfortunately their culture often is less tolerant of failure and learning from failure as the natural sciences.  

 

Ah - the distance.  Measurements of well under a centimeter have been made.   Precision measurements show that the Moon is slowly becoming more distance...  3.8 centimeters a year - about an inch and a half.  Oddly enough the diameter of each retroflector in a mirror array.
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¹ I have the odd habit of telling people what star is roughly the distance it would take light to travel to Earth ..  light leaving there when they were born would be arriving about  now.   I saw a note one reader just turned 31.  Your star this time around is 61 Ursae Majoris  in the Big Dipper.  It's not terribly bright, but you could see it on a dark night.  There are probably stars closer to the date, but they're brown dwarfs that aren't quite visible given the state of infrared telescope technology.  

² Stagnant air may not be very transparent, but it can be very still an offer good "seeing" if you have enough photons.  The solar physics class labs at Caltech used to be done in the JPL parking lot.  Looking at the Sun through a smog filled sky (at least back then) was just fine as long as the sky was still.  Who would have thought that you can do serious astronomy in Pasadena during the day.

³ The laser puts out 2.3 watts - it would easily blind you coming out of the laser,  but spread over 10 square meters would be somewhat safe and on the Moon would be very weak.

 

listen to the mirrors streaking overhead

 

 I've seen it rainin' fire in the sky

 

Ah the Perseids - My favorite meteor shower.  The peak falls somewhere on the 11^th or 12^th of August.  That usually means you can be out all night without a jacket.  If you're in a very dark area on a moonless night sometimes you'll see two hundred in an hour.

 

Comets are the Pig Pens of the Solar System.  Not enough mas for gravity to form into anything solid and spherical, the stuff they're made of tends to boil away as they heat up.  Warm one enough and it's dust trail thickens enough to form a tail or two .  The Tuttle-Swift comet is youthful enough to be extra dusty and the Perseid shower is just the Earth passing through it's dust path.

 

A bright moon marred this year's shower..  even in the mountains counting forty probably required exceptional eyes.  I'm happy with a few, but the sky was cloudy.  Time for Plan B.  I'd listen to them. 

 

Perseid meteors are tiny little things - usually about the size of a grain of sand - that are booking along at about 59,000 meters per second (132,000 miles per hour) when they hit the atmosphere.  They're gone in a flash, but the friction heats them up so much that they ionize - their atoms losing an electron or two. This ionized plasma trail is electrically conductive and makes a dandy radio reflector.

 

The trick is to aim an antenna at VHF or higher frequency station just over the horizon.  The signal won’t make it to you unless, say a reflector just happened to show up somewhere between you and the station.

 

 

I started listening to meteors as a kid in Montana.  At the time Great Falls only had two FM stations.  Edmonton had several including one that was well separated in frequency from anything in Lethbridge or Calgary. I’d point a directional antenna Northish towards Edmonton their frequency and wait.  You'd hear bursts of Canadian radio from one to ten seconds long.    It was clear why I never dated in high school.    

  

 

I still listen to the trails on cloudy nights.    Last night a highly directional antenna was pointed towards a very powerful 61.26 MHz transmitter in Timmins, Ontario (CITO).  The plot on the top is frequency (horizontal) with signal strength in decibels (vertical)  Under it is a scrolling time-stamped “waterfall” plot with frequency along the horizontal axis and color coding for signal strength.  The first meteor trail  was about six seconds long and dab smack at 61.260 MHz  - Timmons coming in via a Perseid!  

 

The plot just under it is a much larger meteor that left a trail lasting over over two minutes. (visually something like this could last as long as twenty seconds)  It was large enough that a bit of it may have made it to the ground.  It would have been bright - undoubtedly brighter than any star or planet. 

 

 

The idea of using mirrors in the sky to communicate isn't new.²  In the early days of satellites it was thought active communication satellites might not be good enough for video and other large bandwidth applications.  Echo was a passive communication satellite.  A metalized balloon about a hundred feet in diameter orbiting about a thousand miles up.  I remember watching it as a kid - it's large reflective surface made it a very bright object in the evening sky.  

 

 

Microwaves were bounced off Echo -- the idea being to have a series or regularly spaced balloons in orbit to allow continuous communication.  As with any technology there were some interesting problems and it wasn't a surprise that Bell Labs was involved with an interesting ground station at Crawford Hill in Holmdel, New Jersey.  

 

for the history of technology buffs  here's an old film on Project Echo

 

 

 

After the Echo program a couple of Bell Labs radio astronomers were using the antenna to  investigate some stubborn radio noise that just wouldn't go away.  They'd point the antenna anywhere in the sky, but wherever they went, there it was.  They double-checked all of their equipment including removing a layer of white organic dielectric material in the twenty foot horn antenna (bird poop). The signal's wavelength corresponded to the microwave spectrum a blackbody would give about three degrees Kelvin -- just above absolute zero.  Only one explanation was plausible.   It turned out to be a cosmic background radiation.  A microwave radiation that is everywhere - the detectable remnant of the Big Bang.  Penzais and Wilson received the Nobel Prize in Physics for the discovery.   A surplus antenna helped change our view of the Universe.

 

 

I continued watching Perseids for five hours.  It  maxed out at about 60 an hour - more than I would have seen visually without the clouds .  Not close to my record, but that's another story.  

__________

 

¹ You can figure out their composition by studying the spectrum of their final light.  Meteorites are those large enough to survive the trip to the Earth.  They are usually at least a few grams at first.  

 

² I won't go into meteor scatter communications, but it's been used in trucking and remote sensing.

 

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Recipe corner

 

Tomatoes are finally great!  I've noted this one before, but it's a keeper and someone just requested it again

 

Simple Summer Pasta and Tomatoes

Some time ago I had a very simple tomato and pasta dish. The tomatoes were
in chucks and not really cooked. It would only work if they were perfect so
I gave it a try. Here is about what I did. This would be enough for two
hungry people or four people if served as a side course. 

Two really amazingly blimpishly ripe tomatoes that are going to have great
flavor. I would go with an heirloom tomato as the new ones have so much
goodness bred out of them. My guess is I had maybe about one and a half
pounds of tomato. Chop these into half inch pieces and scape them into a
big enough bowl (how is that for precision?) be sure and get some of the
juice that is sitting on the cutting board.

Pour some good extra virgin olive oil on them. Maybe two glugs (another quality
measurement). Put a good amount of a good finishing salt (Malden is great) and freshly ground pepper on them stirring to mix. Let them sit.

Start some water boiling for the pasta and throw some salt in. Cheap salt
of course

Now chop a strong red onion or some scallions into slivers. Maybe about a
quarter cup

Chop a handful of good arugula

Cook about a half pound of pasta and try to stay away from the marinating
tomatoes

Place the onions on top of the tomatoes spreading them out, then make a layer
of arugula choppings

Now dump the pasta on top of the layered mixture in the bowl and leave it
for a two or three minutes. To deal with the frustration grate some good
cheese for a topping and top it. (I prefer it without cheese, but most people probably want it). The heat from the pasta is slightly cooking the ingredients beneath,  just barely, but perfectly enough. 

Now mix it all up and serve.

 

extended reality at 78°

 Many of you spend a lot of time traveling around the world.  While the act of travel can be frustrating, new places, people and experiences dramatically richen our lives.  But this usually only makes use of our normal everyday senses.  We're missing so much. Human vision is only a tiny window into the electromagnetic spectrum that surrounds us.  The same for hearing.  And we only experience narrow time.   Events can be too fast or slow for us to notice - global warming for example.   Size is a problem - we can't see the small and only see tiny bits of the large.  And the version of reality our brain assembles goes through a lot of filtering and computation.  

 

Not that this is bad.  The richness of the bit of Nature we perceive wobbles the mind.  And our species is clever enough that we've learned to extend our senses and find new beauty everywhere.   Even the world near your home can be as exotic as any place you can travel on the planet.  You just need to be a bit curious.

 

I live next to a large piece of swampy lowland with terrible drainage.  It's classified as a wetland with development not be allowed this century.  Working out of the home for the past 15 years I've come to know it.  I make a point to spend at least an hour walking in the woods around noon every day no matter the weather.¹  You develop a sense for what a season means.  I've learned we have six distinct periods rather than four.   You keep a diary and make drawings.  With time longer term signals begin to emerge ..  patterns different from seasons. You begin to experience longer time.  

 

My iPhone has become a tool that allows a bit of time compression and expansion.  Nothing dramatic, but much better than what my brain does and worth playing with if you have some patience, a tripod and an app or two.  You can hack that old digital camera and make it sensitive only to infrared light.  Or load that old film camera with film sensitive to the near ultraviolet and find out that humans have stripped patterns on their skin.²   UV is a fun way to look at flowers.  Some pollinating insects are attracted to UV and many flowers have hidden patterns to attract them.  I had a discussion with a gardener who was planning a public garden with a design that would be apparent only if you looked at it in the ultraviolet. 

 

A field microscope is an amazing, to paraphrase Steve Jobs, vehicle for the mind.  Rich enough that I need to write about it separately.  Using your smartphone to record and process the images makes them even more powerful.  

 

The same for sound - your smartphone is a powerful computer with a microphone and a display.   I'm doing that just now.  You've probably heard that the rate of cricket chirping changes with temperature.  This time of year the woods are thick with crickets - four species at least.  They can't chirp if it's cooler than about 55°, but the relationship between chirp rate and temperature is nearly linear from 60° to 95°.³  The standard method is to count how many chirps you hear in 15 seconds.  Make a number of measurements - ten is a good start - and take the average.  Add it to 40 and you should be close to the temperature in Fahrenheit.

 

Being simultaneously lazy and ambitious  I wrote a little program that uses the microphone on my MacBook, does a bit of computation, and shows a spectrogram.  Time is displayed on the horizontal axis, frequency vertically.  Loudness is color coded.  This is thirty seconds with the window closest to the woods open.  There are a number of spectrogram apps for smartphones - I haven't played with any, but you should be able to "see" acoustic detail around you to at least this detail.  If you're really serious write and I'll point you towards some serious proam scientific software. 

 

Notice there's a lot of low frequency noise - something to investigate, but later.  The cricket chirps splash across a number of frequencies, but there's a lot of energy around six kilohertz.  In 15 seconds I count 37.  Doing this a dozen times I average 37.3.  I took a thermometer into the woods a few minutes ago and read 78°F..  40 + 37.3 isn't too bad. 

 

There are a lot of interesting bits of biology and social insect behavior going on that prevent the relationship from being very accurate.  This measurement was a bit lucky.  I've done it at a variety of temperatures and two degrees from the thermometer is more common.  If you can identify different species it might be fun to plot air temperature vs chirp frequency for a range of temperatures and see how it varies from species to species.  

 

There's a lot of richness in the signal to investigate - intensity for example.  Even an amateur can learn a lot and amateurs can make an impact in this type of field biology.  A few years ago I saved a link to a WBUR On Point interview on crickets... it's about a half hour long and just plain fun.  And here's a rich collection of annotated cricket recordings.   Chances are you'll learn something - I did. 

 

The world is much richer than any of us can imagine.  Maybe I'll go into fireflies one of these days.  We have at least four species that you can identify by color, brightness and flash pattern.  It wouldn't be impossible to build an identification app for smartphones.  It shouldn't be too hard and you could even use neural nets to learn about them. 

 __________

¹ ask me about walking in an ice storm - I've found some nice kit.  

² Blaschko's lines. The variations are greater within groups we tend to call a "race" than the visual differences we see between ethnic groups with our eyes.

³ Centigrade is much more common, but in a way Fahrenheit is better here as the degree is smaller.  In physics you rarely use either.  

 

the burgess shale and time machines

Two days ago I found myself on the bus out of Manhattan.  The trip was a treat - I had managed a few hours with a dear friend.  As the bus crawled through commute hour traffic I wondered about the odds of deep friendships like these.  The path to this one involves great leaps of serendipity that I easily trace back to watching someone stare at the ceiling in a Connecticut auditorium fifteen years ago..  I asked them why.  If I hadn't the path probably wouldn't have appeared and I wouldn't know several people on this list.  Perhaps there would be other paths. You wonder about chance versus inevitability.   And that leads to much deeper questions

 

I spent a good deal of my teenage years in the wilderness between The Bob and Glacier in Montana and Banff and Jasper in Alberta with a few excursions to British Columbia.  Meeting two physicists in a small cosmic ray station by chance on Sulphur Mountain in Banff that was one of the sparks that defined my education, but when you're surrounded by Nature there are many possibilities.  

 

The Burgess Shale in British Columbia is so amazing so as to be borderline magic.

 

I was about fourteen when I met soft rockers - paleontologists - for the first time.  Soft rockers do fossils and this was ground zero.  Canadians are wonderful people and Canadian scientists doubly so.  A slow moving science curious teenager was all they needed.  That afternoon I watched as they opened the rock to fossils that were seeing sunlight for the first time in about 550 million years.  I had seen a few fossils in a museum at the University of Utah, but nothing like these.  In fact one of these was completely new to these experts.  They whooped like kids.  It was the first time I saw the ecstasy of discovery. I like Canadians.  

 

The neat thing about this deposit and a few others nearby is they're wonderfully preserved records of the Middle Cambrian.  Even down to soft tissued plants and critters.  You've probably heard the term 'Cambrian Explosion.'  It was a relatively short period when most of what we'd call animals appeared.  It was explosive in that the rate of diversification was far larger than anything seen on Earth.  The Burgess Shale is the best recording device for the period, so paleontologists and, more recently, paleoclimatologists are on it like flies at a picnic.

 

Soon afterward much of this diversity abruptly disappeared.  There were so many paths life could have taken - some completely bizarre.  The question that gnaws on you is what if you could press rewind on time ...  what if you when back to the middle of the Cambrian and let time run forward again.  How would life evolve?  Would we exist?

 

It's a delicious question that seems purely theoretical at first glance.  Many maintain that evolution is pure chance while others maintain there may be an inevitable structure.  But then Richard Lenski came along with a time machine.

 

He had this neat idea.  It hit him that bacteria quickly go through generations.  He decided to look for signals of evolution on a time scale humans might witness.  He started with a dozen populations of E. coli bacteria in early 1988 and watched and waited.  There were problems with funding, electrical outages and the like, but now they're around the 65,000 generation mark with the experiment is still running.  

 

The results were and are amazing.  Some evolutionary adaptations occurred in all of the populations, but others were unique to a single population.  At least one, the ability to use an odd substance as a carbon source in an aerobic environment, created a bizarrely unique form of E. coli. 

 

Other somewhat different approaches show similar results - there is some evolutionary convergence, but divergence is more common - much more common.

 

Lenski won a MacArthur for his work bringing some meaning to what the award is about. He had created something of a time machine for studying evolution. 

 

For me this is a beautiful result.  We're really unique.  That is something to treasure and nurture.  We need to make our condition better and help each other as it's up to us.  As the bus turned onto I-78 I found myself smiling thinking about those deeply improbable and completely unique friendships.

 

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Recipe corner

I've been playing around with ice cream this Summer.  I'm not eating much, but the temptation to do something different is there.    I was caramelizing some onions....  The base is an adaptation of one of the standards...

 

Caramelized Onion Ice Cream

 

Ingredients

 

° 1/2 cup of thinly sliced yellow onions

° 2 Tbl unsalted butter

° 1/2 cup white granulated sugar

° 2/3 cup red wine

° 1 orange ..  juice and grate .. set the zest aside

 ° 4 egg yolks

° 1 large egg

° 2 cups whole milk

° 1/2 cup heavy cream

° 1 Tbl balsamic vinegar (go for good here, but not the super expensive 25 year old variety:-)

 

Technique

 

° caramelize the onions in the butter and 1/4 cup of sugar using your favorite method.  Go for deep brown caramelization without burning (I put them in boiling water for about 5 minutes on similar and then drain, dry.  melt butter in a pan, add sugar and then onions,... brown for 15 to 20 minutes)

 ° add wine, OJ, zest and boil until reduced by half.  This smells good

° whisk the egg yolks and egg and remaining sugar until you get a thick uniformly colored mixture. 

° milk and cream to the onions and bring to a boil stirring along the way.  

° SLOWLY add the egg mixture to the hot mix and stir stir stir.

° pour into a new pan and cook until it coats the back of a spoon. Don't let it boil.

° strain to a clean bowl and add the vinegar

° chill to refrigerator temperatures

° churn freeze